The field of this invention is phase-controlled DC motor regulators, particularly of the digital type, which use a power semiconductor section to provide variable amplitude armature current.
According to one embodiment, this invention relates to operation of DC motor controllers including those which utilize a microprocessor or other digital controller. An example of a microprocessor suitable for such application is an INTEL 8096 or 8097 microprocessor such as may be used in the practice of the invention in application Ser. No. 888,780 filed July 22, 1986, for a Digital Phase Synchronizer. Since that application provides a digital signal suitable for phase synchronization which may be utilized by a digital controller to provide phase firing information, it is expressly incorporated by reference herein. An alternative embodiment utilizes dedicated analog and digital logic circuitry to practice this invention.
In phase controlled DC motor regulator systems, it has been observed that there are two effective levels of gain in the power semiconductor output section corresponding, respectively, to the discontinuous and continuous current conduction regions. "Discontinuous current" refers to the condition where armature current starts from zero each time a power semiconductor is "fired" or turned on by the motor regulator. "Continuous current" refers to the condition or region of operation where armature current continues without interruption as successive phases are fired in the power semiconductor section. In the power semiconductor section, a relatively low gain region exists in the discontinuous region and a relatively high gain region exists in the continuous current region. Because of this, it has not heretofore been possible to optimize regulator gain over both the discontinuous and continuous conduction regions while at the same time adjusting the transition point between such regions. In addition, a significant non-linearity within the discontinuous current conduction region has been an obstacle to obtaining optimum regulator performance.